Administrators at Hildebran Elementary School in Burke County are being sued for allegedly failing to alert authorities for years about a teacher who sexually assaulted students and later admitted to posting explicit images of them on the Internet.

Two lawsuits were filed in federal court in Charlotte on Monday by the guardians of unidentified children. They name the administrators, Burke County Board of Education and Michael Andrew Alexander as defendants.

Alexander, long known as “Mr. A.” at the elementary school in the Burke County foothills, pleaded guilty in July 2012 to first-degree sex offense with a child and to taking indecent liberties with a child. He’s serving a nearly 50-year sentence at Central Prison in Raleigh.

One lawsuit filed Monday names former Hildebran Elementary Principal Wendi Barber and another names Linda Bradshaw, the school’s guidance counselor. The suit says both had been informed of abuse during the 2008-09 school year, but failed to act.

Bradshaw and Barber could not be reached for comment Monday.

The suit says a boy was forced to watch images of women and animals having sex. The child was so disturbed by the images that he went home crying, and told his father, who the lawsuit says informed Barber the next day.

“Barber told (the man) there was nothing that could be done about it and otherwise ignored the incident, choosing to keep (the student) in Defendant Alexander’s class for the remainder of the school year,” according to a lawsuit.

The other suit was brought by a young girl who was 8 when she began being sexually abused and filmed at the school, according to court documents. The girl complained to Bradshaw, the guidance counselor, “that she was being teased and bullied by other girls in class for being singled out as Defendant Alexander’s ‘favorite.’ ”

The girl’s lawsuit says the abuse happened at the same time Alexander was abusing other children who told the principal about the acts.

Court documents say Alexander’s crimes might have gone on for more than a decade. Alexander duplicated videos of young girls engaged in sex acts with each other and with adult men. Court documents also said he took illicit pictures of young girls wearing Hildebran T-shirts and distributed them on the Internet.

The suits allege that Alexander told his victims that if they told anyone about what went on, he would come to their houses and kill them and their families. Staff researcher Maria David contributed.